Starting to get a middle-aged brain? Then give it a good workout

Anyone befuddled by the true value of the discount offers in their supermarket, or struggling for a word that stays defiantly beyond the tip of their tongue, will be unsurprised by research last week showing cognitive decline starts in the 40s.

It surprised the experts, as previous studies have suggested we continued to perform at peak efficiency until our 60s. Though we are losing brain cells from the age of 18, for at least a couple of decades of our adult lives we make up in experience what we lose in potential. But the balance begins to change sooner, it appears, than we think.

The finding should serve as an alert for every middle aged adult. Our most important but most neglected organ needs more care. And it is never too soon to start. Playing chess, doing the crossword and learning foreign languages are all valuable. It may be the intellectual challenge of these activities that keeps the brain sharp or it may be the human contact they generate – it is unclear which. Indeed, staying socially engaged, with friends or family, may be a more important way of keeping alert.

Mental health is not just about mental exercise. What is good for our hearts is also good for our heads. High blood pressure, high cholesterol and obesity are the enemies of a quick mind and a daily 30 minutes of physical exercise – walking swimming cycling – its friend. A 2010 study showed people who walked six miles a week had bigger brains, better memories and improved mental function.

Alcohol may oil the wheels of cognition – up to a point – but smoking only clogs them up. The Mediterranean diet of southern France, Italy and Spain, rich in olive oil and red wine, which is known to protect against heart disease and high blood pressure, has also been shown to cut the risk of Alzheimer's disease by 40 per cent. For those who crave a pill, the likeliest candidate is vitamin B, shown in a University of Oxford study 15 months ago to slow the rate of brain atrophy in elderly people by up to half over two years.

But the best advice to ward off premature decline is simple: keep busy.